300 - 10,000

equally

number

Even though humans are unaware of odors that other animals can detect, human's individual olfactory receptors are as sensitive as any animals. The difference lies in the ____________ of receptors they have.

olfactory mucosa

chemical odorants

Like the rod and cone receptors in the retina contain molecules called visual pigments that are sensitive to light, olfactory receptor neurons (ORNs) in the mucosa contain molecules called olfactory receptors that are sensitive to _____________________.